Antirrhinum striatum/pseudomajus

Upon examining the two most recent papers on A. pseudomajus and A. striatum, it becomes evident that the authors1_2 describe a regulatory network in the context of molecular genetics. This network encompasses not only individual organisms but also entire populations and their interactions with both biotic and abiotic environments.

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They state, «There are no obvious difference in the physical environment or pollinators in the transition of yellow and magenta flowered populations.»
In addition, a clinal transition between the populations with different flower coloration is postulated. The flowers themselves also show gradual pigment differences from proximal to distal in the petals.
The text focuses on the accurate formation of molecular gradients that do not have any clear connection to natural selection.
These findings are interesting in that one should go into more detail about these regulatory networks and gradient formation in the petals together with these steep clines in the allele frequencies across the transitional zone. Natural selection is left out for the time being.

We also reviewed the PhD thesis of Hugo Tavares (2014). He suggests that the hybrid zone might be approximately 100 years old, and the variation between the R1 and r1 loci could potentially be found in some introns of the corresponding gene.

A)

We have drawn a substitute circuit diagram (model presentation) that can plausibly explain all molecular genetic conditions for ROS1. Since the exons of ROS1 (1-3) do not differ in the two subspecies A.m. pseudomajus and A.m. striatum, it is evident that the repetitive sequence located in the intron can play a decisive role in the activity of the MYB. There are two varieties of repetition: either poly TAA in A. pseudomajus or poly TTA in striatum. In the middle of the picture, one will find an internal slider, which, depending on its two extreme positions, either induces uniform sequences or does not, if the triplets are all TAA, resulting in a dominant factor of ROS1. If all triplets are of the structure TTA, the recessive factor is the result (ros1). The MYB factor is then not active. Heterogeneous triplets also occur, which means that the slider occupies a middle position. Even with a hybridization of both forms, this system can also override the gene activity at this position in F1. and F2 plants.  

B) There are more sliders!

Circuit diagram together with Fst Divergence drawn from Tavares 2014.
The extreme points of the graph correspond to short tandem repeats (STRs) of ROS1,(2) and EL. In the substitute circuit diagram at the bottom, the three sliders mark a magenta red flower. Through a slight change in the length of the STR strings, every possible combination can be attained. The lowest extreme is ros1, EL, which is tuned in by yellow flowers.
These findings demonstrate a second and more sophisticated avenue to get the fittest clue in the field for altering floral shape and color in the Catalan Snapdragon.

rolfy July 18 2025

see also The Pushmi-Pullyu-Code

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